نبذة مختصرة : The purpose of this study was to compare dynamic stability and landing kinetics, on land and in water, between young and middle-aged adults performing plyometric exercises. Twenty adults were asked to volunteer: Young = 24.40 ± 2.63 years, n = 10 and middle-aged = 46.80 ± 3.05 years, n = 10. Participants performed three plyometric exercises (countermovement jump, squat jump, and drop landing) on land and in waist-deep water. Dynamic stability was assessed during landing for each exercise using a time to stabilization (TTS) paradigm. Kinetic measures included time to peak force, peak force, rate of force development (RFD), and impulse. Data were collected via a waterproof force plate positioned on an adjustable-depth pool floor and analyzed with a 2 (age) X 6 (condition) repeated measures ANOVA. Results revealed TTS was greater on land (1.45 ± 0.12s) than in water (1.35 ± 0.12s) for two jumps (p = 0.01). Peak force, RFD, and impulse were greater on land (33%-36%) (p < 0.01). Time to peak force was lower (20%), while normalized peak force (15%) and RFD were greater (28%), in the middle-aged compared to the young group (p = 0.04). Results indicate that young and middle-aged adults display improved dynamic stability and are exposed to lower absolute impact forces in water. The effect of age indicates middle-aged participants tend to display greater loading rates and peak forces when compared to the younger group, suggesting landing patterns that may be harmful.
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